How to use 77Ghz single-chip mmWave sensor to achieve automatic parking

Publisher:温暖拥抱Latest update time:2019-02-21 Source: 作者:德州仪器Kishore Ramaiah Reading articles on mobile phones Scan QR code
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Have you ever spent time looking for a parking spot at a shopping mall or grocery store, wishing you could just drop off at the entrance and park yourself, especially if it ’s raining or extremely hot ? How much time would you save if you didn’t have to look around for a parking spot? (Or how much would you save if you didn’t have to pay for valet parking ?). Self-parking will soon become a reality, and automakers are using millimeter wave (mmWave) radar sensors to make it happen.

You might be wondering: do surround cameras and ultrasonic sensors already enable parking? Today’s sensors can provide parking assistance , which means the driver still has to make a judgement call based on the feedback from the sensors . So the car is still not fully autonomous.

Autonomous parking needs to first identify an empty parking space or "free space" at a distance of about 40 meters. This is its "search mode". Once an open space is identified, the car needs to maneuver into it and park, which is called "parking mode".

To enable automated parking, sensors should be able to detect objects ranging from 3 cm to over 40 m across a wide field of view, including other vehicles, curbs, and pedestrians, in all environmental conditions. mmWave sensors help achieve this by accurately detecting smaller objects at distances less than 25 cm , such as metal bars protruding from the ground , which may not be effectively sensed by other sensing modalities . mmWave sensors can also continue to operate in a variety of weather and lighting conditions.

Sensor Installation

Installing sensors in cars is a major challenge today. Since mmWave sensors can be easily installed behind the bumper, car owners do not need to drill holes in the body or chassis. The ability of mmWave to pass through solid materials such as plastics and bumpers without hindrance allows for standardized installation regardless of car manufacturer or car model . The number of sensors required to achieve 360-degree sensing capabilities around the car is also much smaller than other sensing modalities. Only eight sensors are required around the car to achieve 360-degree sensing, as shown in Figure 1.

1

Figure 1: mmWave sensors can provide 360-degree sensing around the car to enable automated parking applications

Multi -mode sensor

Automatic parking is achieved by repurposing existing front and rear corner radars (multi-mode). When the car is in driving mode, these sensors can be used as blind spot detection sensors or lane change assist sensors, which can support detection of cars in other lanes within a distance of 80 meters . When the car is in search or parking mode, the configuration of the sensors changes dynamically to enable sensing of close objects, ranging from 40 meters to less than 10 cm to match the range of parking applications. Multi-mode obstacle detection sensors for the doors can also be used for parking applications. Based on these characteristics , mmWave sensors are becoming increasingly attractive to top automakers. Table 1 lists the advantages of using mmWave sensors for automatic parking applications.

characteristic



Advantage



Long detection range



Senses pedestrians and other objects at a distance greater than 40 meters



Wide field of view



Perceiving objects in the 3D space around the car



Repurposing corner radar sensors



Reduce the number of sensors required at the system level



Multi-mode capability



Dynamic sensing of objects at 40m or 5m

Table 1: System-level benefits of using mmWave sensors for automated parking applications

The AW R1 843 from Texas Instruments (TI) is a 77 GHz single-chip mmWave sensor that integrates digital signal processing, memory, and a radar acceleration unit to enable automated parking applications, as shown in Figure 2.

2

Figure 2: Components of the AWR1843 parking chip

Table 2 shows the application advantages of AWR1843 :

characteristic



Advantage



Three transmitting antennas



Detecting objects in the azimuth and elevation planes



DSP and on-chip memory



Efficiently process complex algorithms on-chip



Radar Accelerator Unit



Perform Fast Fourier Transform operations in hardware to speed up the process



5 degree phase rotator per transmit antenna



Perform beamforming to enhance object detection

Table 2: AWR1843 device features and application advantages

Automakers and top OEMs are increasingly adopting mmWave sensors to provide various driver assistance and automatic parking features. This is mainly due to the features and advantages that mmWave offers - higher integration, (meaning smaller size) . It can help with autonomous driving. 


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